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PI KINK BASES. 713
constanl for the same individual. According to Siven,1
with purine-free
diet the elimination of purines is lowest at night and highest in the morn-
ing hours. Rest and work do not show any positive difference. As
the four true nuclein bases have been treated in Chapter II, it only
remains to describe the special urinary purine bodies.
HX—CO
I I
Heteroxanthine, CeHjNjOi, 7-monomethylxanthine, OC C.N.CHj, was first
I I’
\ch
detected in the urine by Salomon. It is identical with the monomethylxan-
thine which passes into the urine after feeding with theobromine or caffeine.
Salomon and Xeuburg 2
found heteroxanthine in the urine of a dog fed entirely
upon meat, and this was probably formed by a methylation in the body.
Heteroxanthine crystallizes in shining needles and dissolves with difficulty
in cold water (1592 parts at 18° C). It is readily soluble in ammonia and alkalies.
The crystalline sodium salt is insoluble in strong caustic alkali -(33-per cent) and
dissolves with difficulty in water. The chloride crystallizes beautifully, is rela-
tively insoluble, and is readily decomposed into the free base and hydrochloric
acid by water. Heteroxanthine is precipitated by copper sulphate and bisul-
phite, mercuric chloride, basic lead acetate and ammonia, and by silver nitrate.
The silver compound dissolves rather easily in dilute, warm nitric acid; it crystal-
lizes in small rhombic plates or prisms, often grown together, forming charac-
teristic crosses. Heteroxanthine does not give the xanthine reaction, but does
give Wiedel’s reaction, according to Fischer (see Chapter II).
CH3 .N—CO
I I
1-Methylxanthine, CoHsNA, OC C.XH , was first isolated from the
I II \rH
HN—C.N/’
urine and studied by Kruger, and then by Kruger and Salomon. 3
It is diffi-
cultly soluble in cold water, but readily soluble in ammonia and caustic soda,
and does not give an insoluble sodium compound. It is readily soluble in dilute
acids, and it crystallizes from its acetic-acid solution in thin, generally hexagonal
plates. The chloride is decomposed into the base and hydrochloric acid by
water. 1-methylxanthine gives crystalline double salts with platinum and gold.
It is not precipitated by basic lead acetate, nor when pure by basic lead acetate
and ammonia. With ammonia and silver nitrate it gives a gelatinous precipitate.
The silver-nitrate compound crystallized from nitric acid forms rosettes of united
needles. With the xanthine test with nitric acid it gives an orange coloration
on the addition of caustic soda. It gives Weidel’s reaction (according to Fischer)
beautifully.
CH3 .X—CO
Paraxanthine, C7H8N4O2, 1.7-dimethylxanthine, OC C.XCH3 , urotheo-
HX-C.X/’CH
bromine (Thudichum), was first isolated from the urine by Thudichum and
1
Skand. Arch. f. Physiol., 18.
2
Salkowski’s Festschrift, Berlin, 1904.
• Kruger, Arch. f. (Anat. u.) Physiol., 1894; Kruger and Salomon, Zeitschr. f.
physiol. Chem., 24.
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